An electrochemical impedance aptasensor based on selenomolybdate nanodot/antimonene hybrid for platelet-derived growth factor-BB.

The aim of the present study was to design a unique bioelectrode for the quantitative analysis of a potential cancer biomarker, platelet-derived growth factor-BB (PDGF-BB), which can be used for the early detection of cancer. We report the fabrication of succinic acid-capped selenomolybdate polyoxometalate nanodots, POM (SA), decorated antimonene hybrid film on glassy carbon as a suitable bioelectrode. Antimonene nanosheets, synthesized by the chemical exfoliation of antimony provided a large surface area for the symmetric dispersal of POM (SA) nanodots, resulting in site-specific covalent immobilization of the aptamer, PDGF-BB. A comprehensive electrochemical immunosensing investigation was performed on the electrode for sensing of a target antigen, Ag-PDGF-BB. The sensitivity, selectivity, and reproducibility of the bioelectrode were investigated using a best-fit equivalent circuit model that fitted the impedance response. The bioelectrode showed a linear impedimetric response in a broad range for Ag-PDGF-BB (10 pM to 100 nM in pH 7.4 PB) with a limit of detection of 3.5 pM and sensitivity of 80 Ω cm2 per decade. The response sensitivity of the POM(SA)/antimonene hybrid based bioelectrode toward PDGF-BB was approximately ∼1.8-fold higher than that of the POM(SA) only modified bioelectrode. The dissociation constant of immunoreaction between the aptamer-functionalized bioelectrode and target Ag-PDGF-BB was 76 nM, indicating a high binding affinity between the aptamer PDGF-BB and target Ag-PDGF-BB on the electrode surface.

Single Frequency Impedance Analysis on Reduced Graphene Oxide Screen-Printed Electrode for Biomolecular Detection.

A biofunctionalized reduced graphene oxide (rGO)-modified screen-printed carbon electrode (SPCE) was constructed as an immunosensor for C-reactive protein (CRP) detection, a biomarker released in early stage acute myocardial infarction. A different approach of single frequency analysis (SFA) study was utilized for the biomolecular sensing, by monitoring the response in phase angle changes obtained at an optimized frequency resulting from antigen-antibody interactions. A set of measurements were carried out to optimize a frequency where a maximum change in phase angle was observed, and in this case, we found it at around 10 Hz. The bioelectrode was characterized by contact angle measurements, scanning electron microscopy, and electrochemical techniques. A concentration-dependent response of immunosensor to CRP with the change in phase angle, at a fixed frequency of 10 Hz, was found to be in the range of 10 ng mL-1 to 10 µg mL-1 in PBS and was fit quantitative well with the Hill-Langmuir equation. Based on the concentration-response data, the dissociation constant (K d) was found to be 3.5 nM (with a Hill coefficient n = 0.57), which indicated a negative cooperativity with high anti-CRP (antibody)-CRP (antigen) binding at the electrode surface. A low-frequency analysis of sensing with an ease of measurement on a disposable electroactive rGO-modified electrode with high selectivity and sensitivity makes it a potential tool for biological sensors.

Electrochemical Impedance Analysis of Biofunctionalized Conducting Polymer-Modified Graphene-CNTs Nanocomposite for Protein Detection.

We report an electrodeposited poly(pyrrole-co-pyrrolepropylic acid) copolymer modified electroactive graphene-carbon nanotubes composite deposited on a glassy carbon electrode to detect the protein antigen (cTnI). The copolymer provides pendant carboxyl groups for the site-specific covalent immobilization of protein antibody, anti-troponin I. The hybrid nanocomposite was used as a transducer for biointerfacial impedance sensing for cTnI detection. The results show that the hybrid exhibits a pseudo capacitive behaviour with a maximum phase angle of 49° near 1 Hz, which is due to the inhomogeneous and porous structure of the hybrid composition. The constant phase element of copolymer is 0.61 (n = 0.61), whereas, it is 0.88 (n = 0.88) for the hybrid composites, indicating a comparatively homogeneous microstructure after biomolecular functionalization. The transducer shows a linear change in charge transfer characteristic (R et) on cTnI immunoreaction for spiked human serum in the concentration range of 1.0 pg mL-1-10.0 ng mL-1. The sensitivity of the transducer is 167.8 ± 14.2 Ω cm2 per decade, and it also exhibits high specificity and good reproducibility.

Ultrasensitive electrochemical immunosensor based on Pt nanoparticle-graphene composite.

We report a protein antibody, Ab-CRP, functionalized Pt nanoparticle-decorated chemical vapor deposition (CVD)-grown graphene on glassy carbon electrode, as a bioelectrode, for the quantitative analysis of human C-reactive protein (CRP). Chemical vapor deposition was used to grow a polycrystalline graphene film on copper and was mounted over a glassy carbon electrode after copper etching through π-π stacking. Ab-CRP was covalently immobilized on mercaptopropionic acid (MPA)-capped Pt nanoparticles that were covalently anchored over the graphene to form a bioelectrode. The bioelectrode was characterized by scanning electron microscopy, cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). A detail EIS study was conducted on the bioelectrode towards the quantitative detection of the target Ag-CRP in phosphate-buffered saline (PBS). The optimal electrical equivalent circuit that matches the impedance response of the bioelectrode was studied to delineate the biocompatibility, sensitivity, and selectivity of the bioelectrode. The bioelectrode exhibited a linear response of CRP detection in the range of 10 ng mL(-1) to 10 µg mL(-1) with a sensitivity of 92.86 Ωcm(2) per decade CRP in pH 7.4 PBS.